The present invention relates to internal combustion engine turbochargers, and, more particularly, to controlling the operation of a multiple parallel turbocharger system having variable geometry turbines with discrete adjustment steps.
A limiting factor in the performance of an internal combustion engine is the amount of combustion air that can be delivered to the intake manifold for combustion in the engine cylinders. Atmospheric pressure is often inadequate to supply the required amount of air for proper operation of an engine.
An internal combustion engine may include one or more turbochargers for compressing a fluid to be supplied to one or more combustion chambers within corresponding combustion cylinders. Each turbocharger typically includes a turbine driven by exhaust gases of the engine, and a compressor driven by the turbine. The compressor receives the fluid to be compressed and supplies the compressed fluid to the combustion chambers. The fluid compressed by the compressor may be in the form of combustion air only, or may be a mixture of fuel and combustion air. Through the use of a turbocharger, the power available from an engine of given size can be increased significantly. Thus, a smaller, less expensive engine may be used for a given power requirement, and power loss due to, for example, changes in altitude, can be compensated for.
To provide an adequate flow of combustion air, it is known to provide two or more turbochargers in a parallel relationship. Parallel turbines each receive a flow of exhaust gas from the engine exhaust manifold to provide motive force to the turbines of the turbochargers. Compressors of the turbochargers receive gaseous fluid to compress, and discharge compressed fluid for use in the combustion cylinders.
In an exhaust gas turbocharger, exhaust gas flow and turbine design determine turbine performance, and thereby compressor performance and turbocharger efficiency. Vanes in the inlet throat or nozzle of the turbine can be used to affect flow characteristics through the turbine, and thereby the turbine power generated for a given flow. If the engine is to be operated at or near full load during most of its operating cycle, it is not difficult to design the turbocharger for efficient performance. However, if the engine is to be operated at significantly less than full load for extended periods of time, it becomes more difficult to design a turbocharger that will perform well. Desirably, the turbocharger will provide the required level of pressure boost, respond quickly to load changes, and function efficiently, at both high load and low load conditions.
For an engine having a wide range of operating load, it has been know to size the turbine for proper performance under full load conditions. A problem with this approach is that the turbocharger responds slowly at low speed, and the boost pressure available at low engine speeds is minimal. As an alternative, it has been known to provide a turbine design that exceeds the power requirements at full load, and to use a waste gate to bypass excess exhaust gas flow after the turbocharger has reached the desired boost level. An xe2x80x9cundersizedxe2x80x9d turbine of this type will provide greater boost at lower load conditions, and will respond more quickly at lower speeds, but engine back pressure is increased and the energy in the bypassed exhaust flow is wasted.
Turbocharger performance can be controlled by the use of what are known as variable geometry turbines. In a variable geometry turbine, structures of the turbine affecting gas flow can be altered to impact the turbine performance and thereby the overall turbocharger performance. Frequently, the adjustment is at the inlet of the turbine, and may include vane adjustments or nozzle opening adjustments. Some types of variable geometry turbines operate only as discrete steps in nozzle area. Some utilize separate, distinct nozzles of differing area. Operation of multiple parallel turbochargers during a nozzle adjustment cycle is difficult. Surge, excessive exhaust temperatures and excessive turbocharger speeds are all detrimental conditions that can occur when operating multiple parallel turbochargers.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the invention, an internal combustion engine is provided with a plurality of combustion cylinders, an exhaust manifold coupled with the combustion cylinders, and an intake manifold coupled with the combustion cylinders. A plurality of turbochargers each includes a turbine having a variable geometry inlet connected to the exhaust manifold and having an outlet, and including a compressor having an inlet and an outlet, the compressor outlet coupled with the intake manifold. A sensor detects operating conditions and provides a signal dependent thereon. A controller is connected to the sensor to receive the signal, and is connected to the variable geometry inlets for sequential adjustment thereof in response to a need for adjustment.
In another aspect of the invention, a turbocharger system is provided for use with an internal combustion engine having a plurality of combustion cylinders, an intake manifold and first and second exhaust manifolds. The turbocharger system has a plurality of turbochargers each including a turbine having a variable geometry inlet connected to the exhaust manifold and having an outlet, and including a compressor having an inlet and an outlet, the compressor outlet coupled with the intake manifold. A sensor detects an operating condition and provides a signal dependent thereon. A controller is connected to the sensor to receive the signal, and is connected to the variable geometry inlets for sequential adjustment thereof in response to a need for adjustment.
In a further aspect of the invention, a method of operating an internal combustion engine is provided with steps of providing a plurality of combustion cylinders, an exhaust manifold and an intake manifold; transporting exhaust gas from the combustion cylinders to the exhaust manifold; providing a plurality of turbochargers, each turbocharger including a turbine having a variable geometry inlet and an outlet, and a compressor having an inlet and an outlet; providing adjustment means for adjusting positions of the variable geometry inlets; rotatably driving the turbines with exhaust gas introduced at the turbine inlets; introducing combustion gas at the compressor inlets; transporting combustion gas from the compressor outlets to the intake manifold; sensing operating conditions; controlling the adjustment means in response to at least one of the operating conditions; and adjusting at least some of the variable inlets sequentially.
In yet another aspect of the invention, a method for operating multiple parallel turbochargers for an internal combustion engine, is provided with steps of providing a variable geometry turbine for each turbocharger; sensing operating conditions, determining a need to adjust the variable geometry turbines; and adjusting the variable geometry turbines sequentially.